Classification Based on Buoyancy

Q. The density of air at STP is 0.0013g/ml. Its vapour density.

Q.

Which pair of substances among the following would float in a tumbler half-filled with water ?

(a) Cotton thread, thermocol

(b) Feather, plastic ball

(c) Pin, oil drops

(d) Rubber band, coin

Q. If air contains N2 and O2 in volume ratio 4:1, the average vapuor density of air is

Q. Submarines use the principle of ‘neutral buoyancy’ to move in the water. State true or false.

1. True
2. False

Q.

Question 18

During summer holidays, a group of children collected a lump of salt, green grass, broken glass piece, a small thermocol box, pen, iron nail, glass marbles, hair, naphthalene ball, a piece of sugar candy (mishri) and tried to group them on the basis of properties given in table. Help them in filling the table.

$\begin{array}{ccccc}\text{Name of the}& \text{Appearance}& \text{Transparency}& \text{Floats/Sinks}& \text{Soluble}/\\ \text{Material}& \text{(Hard/Soft)}& \text{(Transparent}/& \text{in water}& \text{insoluble in}\\ & & \text{Translucent/Opaque)}& & \text{Water}\\ ..........& ..........& ..........& ..........& ..........\\ ..........& ..........& ..........& ..........& ..........\end{array}$

Q.

Which among the following will float on water?

1. Needle
2. Iron nail
3. Stone
4. Oil

Q. As a balloon rises in the air its volume increases and at the end, it acquires a stable height and cannot rise any further. State true or false.

1. False.
2. True.

Q.

Question 4 (iv)

State whether the statement given below is True or False.

A piece of wood floats on water

Q. Why does an object float or sink when put in water?

Q.

How can we determine whether an object will float or sink in water? Explain with examples. [3 MARKS]

Q.

Question 15

Take a small cotton boll and place it in a tumbler/bowl filled with water. Observe it it for at least 10 minutes. will it float or sink in water and why ?

Q.

Question 6

List all items known to you that float on water. Check and see if they will float on an oil or kerosene.

Q.

Give one example each of the following combinations of properties. [5 MARKS]

$\begin{array}{cc}\text{1.}& \text{Lustrous and Hard}\\ \text{2.}& \text{Soluble and Opaque}\\ \text{3.}& \text{Translucent and Soft}\\ \text{4.}& \text{Insoluble and Floating}\\ \text{5.}& \text{Sinking and Transparent}\end{array}$

Q. Which of the following sinks in water?

1. Wooden block
2. Piece of wax
3. Plastic ball
4. Glass marble

Q. A leaf on water while a coin in it.

1. dissolves
2. sinks
3. floats
4. dissapears

Q. The density of tap water is less than that of seawater. If an object is immersed completely in both one by one, what will its loss in weight be?

1. More in sea water.
2. Zero in seawater but not so in the case of tap water.
3. Less in sea water.
4. Equal in both the cases.

Q. The ______ sinks in water while the _______ floats.

1. ship, boat
2. soap cake, soap case
3. nail, hammer
4. paper, paper boat

Q. Most metals sink in water as they have density _______ water.

1. lower than
2. higher than
3. comparable to
4. same as that of

Q. Which of the following substance will float in water?

1. Coin
2. Steel spoon
3. Plastic ball
4. Coloured pebbles